Linear optical properties of Si surfaces and nanostructures

We review the optical responses of Si surfaces and nanostructures (porous S i) as measured by reflectance-difference spectroscopy and spectroscopic ell ipsometry. We discuss a model of the optical responses of surfaces where th e surface contributes indirectly through many-body effects and by dynamical ly modifying an apparent bulk response as well as directly usually involvin g surface states. Indirect processes dominate the spectra of chemically sat urated Si surfaces. The results suggest a close relationship among the opti cal properties of surfaces, interfaces, and nanostructures, and show that a complete description requires time dependences and many-body effects to be included.